Apparatus for roasting coffee beans and method for controlling roasting temperature

ABSTRACT

An improved apparatus and method for the hot air roasting of coffee beans is provided and includes structure for inhibiting contaminants from entering the hot air stream used in the roasting of coffee beans, structure for obtaining a uniform roast of the coffee beans, unitary structure for mounting a handle to a roasting chamber and removably and releasably mounting a cover to the roasting chamber, structure for initiating a roasting cycle and terminating the roasting cycle for a predetermined cooling period at any point during the roasting cycle, structure for double sealing a cover to a roasting chamber, structure for assembling a vessel, a metallic base, and a plastic mount ring into an integral roasting chamber, structure for releasably and removably mounting a roasting vessel to a main housing, dual filters for preventing the blockage of a hot air stream through a hull and chaff collector, and a “fan based” method for controlling the roasting temperature.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.09/303,709, filed Apr. 30, 1999, now U.S. Pat No. 6,195,912.

FIELD OF THE INVENTION

This invention relates to apparatus for roasting coffee beans, and morespecifically, to relatively small coffee bean roasters that rest on acounter-top or table during operation, such as coffee roasters that areprimarily intended for use in the home or for roasting relatively smallbatches of coffee at a restaurant or coffee shop or for sample cupping.

BACKGROUND OF THE INVENTION

Recent years have seen an explosion of interest in gourmet coffeeproducts and the interest has not been limited to the purchase ofcoffee-based beverages from vendors who prepare the beverage on premiseand purvey it to consumers over the counter. Similarly, the interest hasnot been limited to gourmet blends, coffee that may be purchased alreadyground, and then brewed in the home. Many consumers desire the ultimatein freshness and flavor and have taken to roasting their own beans andthen grinding them shortly before the coffee brewing process isinitiated.

As a consequence, there is an increasing market for coffee roastingapparatus that may be used in the home. A variety of coffee roastingapparatus have been devised to meet this market. Examples of such acoffee roasting apparatus are illustrated in U.S. Pat. No. 5,564,331issued Oct. 15, 1996 to Song, and in application Ser. No. 09/134,324,filed Aug. 14, 1998, titled “APPARATUS FOR ROASTING COFFEE BEANS”, toKelley, the entire disclosures of which are herein incorporated byreference. These roasters work well for their intended purpose, butthere is always room for further improvement.

For example, to achieve optimum roasting, it is necessary that the beansbe uniformly heated. If the heating is not uniform, some of the beansmay pop early in the roasting process and others, not at all.Consequently, uniform flavor cannot be obtained. Thus, there is acontinuing need to improve the uniformity of heating, and/or provideuniformity of heating in connection with other improvements.

Similarly, it is desirable for the roasting temperature to be accuratelycontrolled to assure maximum husk removal, as well as proper flavordevelopment, which cannot occur if the roasting temperature is eithertoo low or too high. The roasting temperature can be affected in anumber of ways. For example, coffee roasters intended for home use havegenerally subjected the coffee beans to an air stream that is heated byan electrical resistance heater, the heat generation of which can besignificantly affected by variation in line voltage.

To control the electrical resistance heater, and/or accommodate thevoltage fluctuations, at least one coffee roaster has energized andde-energized the electrical resistance heater by opening and closing arelay. However, this may reduce the life of the relay and may providefluctuations in the roasting temperature that are less than optimum.

Another common concern for home use coffee makers is the consistencyfrom one roasting cycle to the next roasting cycle, which may occurseveral days apart. Typically, coffee roasters are provided with amechanical timer that must be turned to the desired roasting time eachtime the roaster is used. It can be difficult to return the mechanicaltimer to precisely the same setting from one operation to the next toachieve the desired roast. Further, because of the time period betweenoperation of the coffee roaster, a user may forget which setting on thetimer has provided the user with the user's desired roast.

Another common challenge for all coffee roasters is the relatively hightemperatures required for roasting the coffee beans. These temperaturescreate a number of concerns, including the safety of the user and thetype of materials that can be used in the roaster to accommodate thehigh temperatures and the costs associated with such materials.

A concern somewhat related to the high temperature of the roasters isthe energy efficiency of such roasters, which can require relativelylarge amounts of power to provide the high temperatures.

Other concerns include the potential for contaminants to enter the hotair stream of the coffee roaster, cooling of the coffee roastercomponents, the convenience of using the coffee roaster, and theappearance and functionality of the coffee roaster components.

The present invention is directed to addressing one or more of the aboveconcerns.

SUMMARY OF THE INVENTION

The principal object of the invention is to provide a new and improvedcoffee bean roasting apparatus, particularly suited for home use.

In one form of the invention, an apparatus for roasting coffee isprovided and includes a housing having an air inlet and an air outletspaced from the air inlet, a coffee bean roasting chamber mounted to thehousing, an electric motor within the housing, a first fan in fluidcommunication with the roasting chamber and driven by the electric motorto create a roasting air flow from the air inlet to the roastingchamber, a heater within the housing to heat the roasting air flow priorto the roasting air flow entering the roasting chamber, and a second fandriven by the electric motor to create an evacuating air flow from thehousing through the air outlet to remove motor generated contaminantsfrom the housing.

In one form, the apparatus further includes a barrier surrounding theair outlet on an exterior surface of the housing to inhibit movement ofmotor generated contaminants from the air outlet to the air inlet afterthe motor generated contaminants are removed from the housing. Thebarrier defines an opening that directs the evacuating air flow awayfrom the air inlet.

According to one aspect of the invention, a roasting chamber is providedfor roasting coffee beans and includes a bottom having at least one airinlet opening to create a substantially vertical air stream into theroasting chamber, a diverter located above the bottom in a position thatis centered in the vertical air stream to redirect coffee beans movingupwardly in the vertical air stream toward a location in the roastingchamber that is remote from the at least one air inlet opening, and atleast one guide surface to guide the redirected coffee beans back towardthe at least one air inlet opening.

In one form, the bottom is planar and the at least one guide surfaceincludes a slant surface that slants downwardly to the planar bottom.

In one form, the at least one guide surface also includes a verticallyextending outer wall, with the slant surface slanting downwardly fromthe outer wall to the bottom.

In one form, the at least one air inlet opening includes a firstplurality of circular holes of a first diameter and a second pluralityof circular holes of a second diameter larger than the first diameter,with the second plurality of circular holes nominally located at anintersection between the planar bottom and the slant surface.

According to one aspect of the invention, a roasting chamber is providedfor roasting coffee beans and includes an outer wall in the shape of abody revolution about a vertical axis, a base including a planar bottomand an upwardly opening, frustoconical side wall extending from theplanar bottom to the outer wall, the bottom and the side wall nominallycentered on the vertical axis, and a mushroom-shaped diverter extendingupwardly from the planar bottom, nominally centered on the verticalaxis. The base further includes at least one air inlet opening extendingthrough at least one of the bottom and the side walls.

According to one aspect of the invention, an apparatus is provided forroasting coffee beans and includes a coffee bean roasting chamber, ahandle for the roasting chamber, a band wrapped around the roastingchamber clamping the handle thereto. The band includes a plurality oframped tabs extending away from the roasting chamber, and a cover forthe roasting chamber. The cover includes a plurality of ramped lands,the lands engaging with the ramped tabs on the band to lock the cover tothe roasting chamber when the cover is rotated relative to the roastingchamber in a first direction, and disengaging from the ramp tabs on theband to release the cover from the roasting chamber when the cover isrotated relative to the roasting chamber in a direction opposite thefirst direction. Thus, the band serves to mount the handle to theroasting chamber and to removably and releasably mount the cover to theroasting chamber.

According to one aspect of the invention, a method is provided forcontrolling the roasting temperature in the roasting chamber of a hotair coffee roaster including an electric heater and a fan that forcesair past the heater to generate a hot air flow into the coffee roaster.The method includes the steps of energizing the electric heater, drivingthe fan at a normal operating speed, monitoring a temperature of the hotair flowing into the roasting chamber, and driving the fan at a coolingspeed that is greater than the normal operating speed in response to themonitored temperature exceeding an upward temperature limit.

In one form, the method further includes the step of returning the fanto the normal operating speed from the cooling speed in response to themonitored temperature dropping below a lower temperature limit.

In one form, the step of powering the fan at a cooling speed includespowering the fan at the cooling speed for a fixed period of time inresponse to the monitored temperature remaining a lower temperaturelimit for the fixed period of time.

In one form, the method further includes the step of de-energizing theelectric heater in response to the monitored temperature remaining abovethe upper temperature limit for the fixed period of time.

According to one aspect of the invention, an apparatus is provided forroasting coffee beans and includes a housing having an air inlet, acoffee bean roasting chamber mounted to the housing, an electric motorwithin the housing, a fan in fluid communication with the roastingchamber and driven by the motor to create a roasting air stream directedto the roasting chamber, an electric heater within the housing to heatthe roasting air stream prior to the roasting air stream entering theroasting chamber, and a control for the motor. The control includes atemperature sensor located in the air stream downstream of the heater.The control is operative to power the motor at a cooling speed inresponse to the sensor detecting a temperature greater than an uppertemperature limit and to power the motor at a normal operating speed inresponse to the sensor detecting a temperature less than a lowertemperature limit. The normal operating speed is less than the coolingspeed.

According to one aspect of the invention, an apparatus is provided forroasting coffee and includes a housing having an air inlet, a coffeebean roasting chamber mounted to the housing, an electric motor withinthe housing, a fan driven by the electric motor to create a roasting airstream directed to the roasting chamber, an electric heater within thehousing to heat the roasting air stream prior to the roasting air streamentering the roasting chamber, a control for the heater and the fan thatis operative to energize the heater and power the motor to drive the fanto provide a roasting cycle, and a switch operably connected to thecontrol to de-energize the heater while running the motor for apredetermined time period in response to activation of the switch by auser during the roasting cycle.

In one form, the control is operative to energize the motor and theelectric heater to obtain a desired roasting cycle based on a settinginput by a user. The control also maintains the setting between roastingcycles absent further input by a user. The apparatus further includes asecond switch operably connected to the control to initiate the desiredroasting cycle in response to activation of the second switch by a user.

In one form, the control is operative to maintain a temperature rangedetermined from the setting for a fixed period of time, with the fixedperiod of time being independent of the setting.

In one form, the control is operative to maintain a fixed temperaturerange for a period of time that is determined from the setting, with thefixed temperature range being independent of the setting.

According to one aspect of the invention, an apparatus is provided forroasting coffee and includes a coffee bean roasting chamber including anupper portion defined by a nominally cylindrical wall that terminates ina nominally circular lip that surrounds an open top of the roastingchamber, and a cover for the open top of the roasting chamber. The coverincludes a preformed resilient seal having a nominally cylindricalportion that blends into a nominally planar portion that extendsradially from the cylindrical portion. The cylindrical portion isadapted to form a seal with the cylindrical wall of the roasting chamberand the planar portion is adapted to form a seal with the circular lipof the roasting chamber when the cover is installed on the roastingchamber.

According to one aspect of the invention, a roasting chamber is providedfor roasting coffee and includes a vessel, a metallic base, and aplastic mount ring. The vessel has an open bottom and is defined by anouter wall in the shape of a body of revolution about an axis. The outerwall includes a radially inwardly extending annular shoulder. Themetallic base is mounted within the open bottom of the vessel and has anouter periphery abutting the shoulder. The base includes at least oneinlet for the introduction of a hot air stream into the vessel. Theplastic mount ring is fastened to the metallic base to clamp theshoulder of the vessel between the metallic base and the mount ring,thereby assembling the vessel, the metallic base and the mount ring intoan integral unit.

According to one aspect of the invention, an apparatus is provided forroasting coffee beans and includes a housing, a motor within thehousing, a fan, a heater within the housing, and a coffee bean roastingchamber. The housing includes an air inlet, a hot air outlet, a radiallyoutwardly facing cylindrical surface surrounding the hot air outlet, anda plurality of circumferentially spaced tabs extending radiallyoutwardly from the radially outwardly facing cylindrical surface. Thefan is driven by the motor to create a roasting air stream which isdirected to the hot air outlet. The heater heats the roasting air streamprior to the roasting air stream entering the hot air outlet. The coffeebean roasting chamber includes a cylindrical wall that surrounds theradially outwardly facing cylindrical surface of the housing with thechamber installed on the housing. The roasting chamber further includesa plurality of circumferentially spaced tabs extending radially inwardlyfrom the cylindrical wall. The tabs on the chamber engage with the tabson the housing to lock the chamber to the housing when the chamber isrotated relative to the housing in a first direction. The tabs on thechamber disengage from the tabs on the housing to release the chamberfrom the housing when the chamber is rotated relative to the housing ina direction opposite of the first direction.

According to one aspect of the invention, a hull collector is providedfor a hot air coffee roasting apparatus to collect hulls and other chaffproduced by the roasting of coffee beans in the coffee roastingapparatus. The hull collector includes a body defining a collection areafor hulls and other chaff produced by the roasting of coffee beans, ahot air inlet to the body for the hot air stream used in roasting thecoffee beans, a hot air outlet from the body for the hot air stream usedin the roasting of coffee beans, a first filter positioned in the bodybetween the hot air outlet and the hot air inlet and having openings ofa first size to filter a first size of hulls and other chaff from thehot air stream as the hot air stream flows from the hot air inlet to thehot air outlet, and a second filter positioned between the first filterand the hot air outlet and having openings of a second size smaller thanthe first size to filter a second size smaller than the first size ofhulls and other chaff from the hot air stream as the hot air streamflows from the first filter to the hot air outlet. Thus, the firstfilter inhibits large hulls and other chaff from clogging the secondfilter, and the second filter inhibits smaller hulls and other chafffrom exiting the hot air outlet.

Other objects and advantages will be apparent from the followingspecification taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a coffee roaster embodying the invention;

FIG. 2 is a diagrammatic, exploded view of the coffee roaster;

FIG. 3 is a bottom view taken along line 3—3 in FIG. 1;

FIG. 4 is an enlarged, fragmentary sectional view of selected componentstaken substantially along line 4—4 in FIG. 1;

FIG. 5 is a plan view of a base for a roasting chamber of the coffeeroaster;

FIG. 6 is an enlarged, fragmentary sectional view taken along line 6—6in FIG. 2 showing the connection of a handle to the roasting chamber ofthe coffee roaster;

FIG. 7 is a top plan view of a hull collector component of the coffeeroaster shown in FIG. 1;

FIG. 8 is a sectional view taken substantially along line 8—8 in FIG. 1showing the hull collecting component and a lid therefor;

FIG. 9 is a schematic of the operating components and control employedin the coffee roaster;

FIG. 10 is a logic diagram illustrating the control logic for obtaininga desired roast in one configuration of the coffee roaster;

FIG. 11 is a logic diagram illustrating the control logic for obtaininga desired roasting cycle in another configuration of the coffee roaster;and

FIG. 12 is a logic diagram illustrating the roasting temperature controllogic for the coffee roaster.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An exemplary embodiment of a coffee bean roasting apparatus madeaccording to the invention is illustrated in FIG. 1 and is seen toinclude four major components, including a power base 10, removablysupporting a coffee roasting chamber, generally designated 12. Achaff/hull receiver or collector, generally designated 14, is located atthe upper end of the coffee roasting chamber 12. The hull receiver 14,in turn, removably receives a lid, generally designated 15. The powerbase 10, the roasting chamber 12, the hull collector 14 and the lid 15are all generally centered on a vertical, central axis 16 of the coffeebean roasting apparatus.

The power base 10 includes a main housing in the form of an assembly 17,a commutated electrical motor 18 having carbon brushes 19 and an outputshaft 20 that rotates about a vertical motor axis 21 and mounts firstand second fans or impellers 22 and 23 for rotation about a motor axis21. The housing assembly 17 includes air inlet openings 24 and airoutlet openings 25 in its underside. The fan 22 is located in acup-shaped housing 26 having intake openings 28 through which air mayflow from the inlet openings 24 in the main housing 17 to the fan 22.

Just above the fan 22, a mica sheet 30 with one or more air flowapertures 32 mounts a heater 34 in the form of a circular, electricalresistance heating element. The heating element 34 is, in turn, held inposition on the mica sheet 30 by an additional mica sheet 36. Atemperature sensor 38, preferably in the form of a thermistor, ismounted on the mica sheet 36 on the side thereof opposite the resistanceelement 34 centered on the axis 16 and thus, in the path of air flow, isdownstream of the heating element 34 and upstream of the roastingchamber 12.

The heating element 34, the sensor 38, and the fan 22 are enclosed in anassembly including the cup-shaped housing 26 along with a second,inverted cup-shaped housing 39 which is secured to the mica sheet 30 andto the cup shaped element 26 by any suitable means, such as a pluralityof circumferentially spaced threaded fasteners 41 (only one shown inFIG. 1), that clamp a ring-shaped seal 40 between the mica sheet 30 andthe housing 26. The cup-shaped housing 39 includes a hot air outletopening 42 through which air heated by the element 34 may be dischargedupwardly. The outlet opening 42 is centered on the central axis 16. Acircular plate 43 having a plurality of circumferentially spacedpie-shaped apertures 44, best seen in FIG. 2, is fixed by deformabletabs to the housing 39 over the outlet opening 42. As best seen in FIG.1, a generally ring-shaped, high temperature sealing element 45 iscentered on the axis 16 and mounted to the housing 39 by an outermostrim of the plate 43 that engages an annular slot 46 in the sealingelement 45. The sealing element 45 includes a radially inwardly directedsealing flange 47 that includes a pair of upwardly directed annular ribs48. The flange 47 and ribs 48 engage a lowermost portion of the roastingchamber 12 to prevent leakage of heated air as it moves from theresistance element 34 upwardly into the roasting chamber 12. Preferably,the sealing element is made from a suitable silicon material. The motoris fixed to the cup-shaped housing 26 by any suitable means, such as aplurality of fasteners 49 (only one shown in FIG. 1). Together, thehousings 26 and 39, the mica sheet 30, the seal 40, the resistanceelement 34, the sensor 38, the fan 22, the circular plate 43, theceiling element 45 and the motor 18 define a heater/motor subassembly 50that is centered on the motor axis 21.

The main housing 17 includes a generally cylindrically shaped,substantially hollow base housing 51 centered on the axis 16, a controlmounting panel 52, and a vessel mounting cover 54. The heater/motorsubassembly 50, is attached to the housing assembly 17 by any suitablemeans, such as by three circumferentially spaced threaded fasteners 56(only one shown in FIG. 1), each of which engages a post 58 formedintegrally with the cover 54. Similarly, the cover 54 and theheater/motor subassembly 50 are attached to the base housing 51 by anysuitable means, such as by three threaded fasteners 60 that engagerespective support post 62 (only one shown in FIG. 1) formed integrallyeither on the cup-shaped housing 26 or on the cover 54. The panel 52includes a lip 64 which extends around the periphery of the panel 52 andengages with mating structures on the base housing 51 and the cover 54to retain the panel 52 to the main housing assembly 17.

The base housing 51 includes a cylindrical wall portion 66 centered onthe motor axis 21 and extending around the impeller 23 and thecommutator 19 of the motor 18. As best seen in FIG. 3, a generallyC-shaped barrier in the form of resilient foot member 67 is mounted tothe bottom of the base housing 50 surrounding the air outlet openings 25and defines an opening 68 that is directed away from the air inletopenings 24. In operation, the fan 23 creates an air flow from theinterior of the housing assembly 17 through the outlet openings 25. Theair flow is directed past the commutator 19 by the wall 66 so that theair flow forces motor generated contaminants, such as carbon particlesgenerated by the brushes 19 engaging the motor commutator through theopenings 25. The foot member 67 directs the air flow, and thecontaminants therein, out through the opening 68 in a direction awayfrom the air inlets 24, as shown by the arrows A to prevent thecontaminants from being drawn back into the interior of the housingassembly 17 through the air inlets 24. The resiliency of the member 67creates a sufficient seal with the counter top on which the roaster isplaced to close any significant leakage path for the carbon particlestoward the air inlets 24.

The cover 54 includes a hot gas outlet opening 70 surrounding theopening 42 and the seal 45 of the heater/motor subassembly 50. Anannular, vessel mounting groove 72 is centered on the axis 16surrounding the opening 70 and is defined by a radially outwardly facingcylindrical surface 74 that is spaced radially from a radially inwardlyfacing cylindrical surface 76. The groove 72 receives a mount ring 82having a cylindrical wall 83 and that is centered on the axis 16 andfixed to the roasting chamber 12. Four equally circumferentially spaced,radially outwardly extending tabs 84 (only one shown in FIG. 1) on thehousing 54 engage a like number of equally circumferentially spaced,radially inwardly extending tabs 85 (only one shown in FIG. 1) on thering 82 extending radially inwardly from the wall 83. The tabs 84 and 85are engaged by placing the mount ring 82 into the groove 72 and thenrotating the roasting chamber 12 and the mount ring 82 about the axis 16relative to the main housing assembly 17 and the groove 72 to lock theroasting chamber 12 to the main housing 17. By reversing the directionof rotation about the axis 16, the tabs 84 and 85 can be moved out ofengagement and the vessel 12 can be lifted from the housing assembly 17.Preferably, at least one set of the tabs 84 and 85 have angled chamfers86 on their leading edges to cause engagement with the other set of tabs84 and 85, as best seen in FIG. 4. It is also preferred that at leastone set of the tabs 84 and 85 have support/stop walls 87 extendingperpendicular from their trailing edges to provide structural supportfor the tabs 84 and 85 and to limit the relative rotation between theroasting chamber 12 and the main housing assembly 17. Further, it ispreferred that the radially inwardly facing cylindrical surface 76include a circumferentially extending relief 88 that receives acircumferentially extending protrusion 89 on the mount ring 82 toangularly orient the tabs 84 and 85 relative to each other when themount ring 82 is inserted into the groove 72. It should be understoodthat the relief 88 should have a sufficient circumferential length toallow movement of the protrusion 89 within the relief 88 when theroasting chamber 12 and the main housing assembly 17 are rotatedrelative to each other to engage and disengage the tabs 84 and 85.

The roasting chamber 12 includes a vessel 90 defined by an outer wall 91in the shape of a body of revolution, preferably a cylinder, centered onthe axis 16 and is preferably made of heat and shatter resistant glass.The vessel 90 includes an upper outlet, generally designated 92 in FIG.2, and an open bottom, generally designated 94 in FIG. 2, with aninwardly extending annular shoulder 96. The open bottom 94 is closed bya lower wall or base 98 that includes a planar bottom 100 that blendsinto an upwardly opening, frusto-conical side wall 101 extending fromthe bottom 100 to the outer wall 91 of the vessel 90. Preferably, thebase 98 is formed from a suitable metal, such as 304 stainless steel. Aresilient, ring-shaped seal 102 is seated between the shoulder 96 of thevessel 90 and an outermost periphery 104 of the lower wall 98.Preferably, the seal 96 is made from a suitable high temperatureresilient material, such as a suitable silicone material. While themount ring 82, the vessel 90, and the lower wall 98 may be fixedtogether by any suitable means, in the preferred embodiment, theshoulder 96 of the vessel 90 is clamped between the outer periphery 104of the base 98 and a radially inwardly extending flange 108 on the mountring 82 by three circumferentially spaced, threaded fasteners 110 (onlytwo shown in. FIG. 1) that extend through holes in the flange 108 toengage threaded bosses 112 in a ring-shaped flange 114 that is integralwith the base 98.

As best seen in FIG. 5, the lower wall 98 includes a plurality of inletopenings 120 formed mostly in the bottom 100 to direct a hot air streamvertically into the chamber 12 from the outlet 43, as indicated by thearrows B in FIG. 1. While the holes 120 may be arranged in a number ofways and may be of any suitable number size and shape, in the preferredembodiment, the holes 120 are circular, and are arranged so that theradially innermost holes 120 are smaller than the radially outermostholes 120, with all the holes 120 being distributed relatively uniformlyabout the central axis of the vessel 90 and the outermost holes centeredat the intersection between the bottom 100 and the wall 101. Thisparticular arrangement provides a relatively high velocity hot airstream at the centermost portion of the base 98 surrounded by a somewhatlower velocity hot air stream from the outermost holes 120. Thisarrangement has proven advantageous in assuring that the coffee beanscirculate relatively uniformly during the roasting process withoutstagnating at any point on the base 98.

The roasting chamber 12 further includes a diverter 124 located abovethe bottom 100 in a position that is centered in the vertical hot airstream from the holes 120 to redirect coffee beans moving upwardly inthe vertical airstream toward a location in the roasting chamber 12 thatis remote from the inlet openings 120, as shown by the arrows C in FIG.1. The outer wall 91 and the frusto-conical wall 101 act as guidesurfaces that guide coffee beans back toward the inlet openings 120after they have been redirected by the diverter 124. Thus, it can beseen that the interaction of the hot air stream generated by the inletopenings 120, the diverter, the outer wall 91 and the frusto-conicalwall 101 creates a recirculating movement of the coffee beans as theyare roasted wherein the coffee beans are continuously circulated fromthe hot air stream to a location remote from the hot air stream and thenback into the hot air stream to ensure a uniform roast of all the coffeebeans. In this regard, in the preferred embodiment, the diverter 124 isa generally mushroom-shaped diverter 124 that extends upwardly from thebottom 100 and is centered on the axis 16. The diverter 124 includes acylindrical stem 126 that blends into a cone-shaped head 128 that istopped by another conical shaped head portion 130. The diverter 124 isattached to the base 98 by a suitable fastener, such as threadedfastener 131. The angle α of the cone-shaped head 128, the diameter D1of the cone-shaped head 128, the diameter D2 of the planar bottom 100,the diameter D3 of the periphery 104, and the angle Ψ of thefrusto-conical wall 101 are all important factors in achieving thedesired recirculation of the coffee beans within the roasting chamber12. For example, the angle α and the diameter D1 of the diverter 124 areimportant in assuring that the coffee beans are directed against theouter wall 91 of the vessel 90, rather than being directed upwards toexit the opening 92 of the vessel 90. By way of further example, theangle Ψ of the frusto-conical wall 101 is important to assure that thecoffee beans return back to the inlet openings 120 after beingredirected by the diverter 124, but not so quickly that the coffee beansaccumulate over the holes 120. While any number of combinations arepossible to achieve the desired results, in the preferred embodimentillustrated in the figures, α is approximately equal to 39°, Ψ isnominally equal to 65°, D1 is nominally equal to 30 mm, D2 is nominallyequal to 32 mm, and the diameter D3 is nominally equal to 115 mm.

In addition to providing a recirculation of the coffee beans thatachieves a uniform roast of all the coffee beans, the diverter 124increases the dwell time of the hot air stream within the roastingchamber 12 by redirecting the hot air stream so that it does not flowdirectly out of the roasting chamber 12. This increases the operatingefficiency of the coffee roaster.

As best seen in FIG. 2, a handle 132 is fixed to the roasting chamber 12by a band 134 that is tightened around the outer surface of the vessel90 by a threaded fastener 136 that extends through the handle 132 toengage the band. More specifically, as best seen in FIG. 6, the bandincludes a pair of flanged ends 138 and 140 that extend into a slot 142in the handle 132. The threaded fastener 136 extends through an openingin the handle 132 and engages with threads on the flanged end 138 topull the flanged ends 138 and 140 toward each other, thereby tighteningthe band to the outer surface of the vessel 90 and engaging the handle132 to the band 134 to mount the handle 132 to the roasting chamber12.As best seen in FIG. 2, a tab 148 on the handle 132 extends into areceiving slot 150 formed on the mount ring 82 to retain the lowerportion of the handle 132 to the roasting chamber 12. In addition tomounting the handle 132 to the roasting chamber 12, the band 134 servesto removably and releasably mount the hull collector 14 to the roastingchamber 12. More specifically, as best seen in FIG. 1, the hullcollector 14 includes a generally ring-shaped mounting member 152 havinga downwardly extending cylindrical flange 154. The flange 154 includesfour equally circumferentially spaced notches 156, each of which has aramped land 157. The notches 156 receive a like number of equallycircumferentially spaced ramped tabs 158 that extend radially outwardlyfrom the band 134 and that are engageable with the ramped lands 157.When the hull collector 14 is rotated relative to the roasting chamber12 in one direction, the hull collector 14 is locked by the engagementof the lands 157 and tabs 158 to the roasting chamber 12. The oppositerotation releases the hull collector 14 from the roasting chamber 12. Inthis regard, it should be understood that the band 134 could be used toremovably and releasably mount any type of cover for the roastingchamber 12, regardless of whether the cover also serves the function asa hull collector 14.

In the preferred embodiment, the band 134 also includes four equallycircumferentially spaced non-ramped tabs 159 that extend radiallyoutwardly from the band 134 to engage the bottom lip of the wall 154 tolimit the downward engagement of the hull collector 14 to the vessel 90resulting from the interaction of the ramped lands and tabs 157 and 158.While the band 134 may be formed of any suitable material, it ispreferred that the band 134 be formed of a suitable stainless steel withthe tabs 158 and 159 being unitary members of the band 134. Further, asbest seen in FIG. 8, the flange 154 includes a circumferentiallyextending notch 160 that receives an upper portion of the handle 132 andhas sufficient circumferential clearance to allow the relative rotationbetween the hull receiver 14 and the roasting chamber 12 to allow thelands 157 and tabs 158 to engage and disengage.

As best seen in FIG. 1, the hull collector 14 also includes a bottomwall 160 connected to the mounting member 152. The wall 160 includes aninnermost flange 162 centered on the axis 16 and defining a central hotair inlet opening 163. The flange 162 is connected to a cylindrical wallportion 164 that is centered on the axis 16 and blends into a planarbottom 166, which in turn blends into another cylindrical wall portion168 of the bottom wall 160. As best seen in FIG. 7, a generally planar,outermost flange 170 of the bottom wall 160 extends from the cylindricalportion 168 and is fixed to the mounting member 152 by any suitablemeans, which in the preferred embodiment is provided in the form of aplurality of circumferentially spaced rivets 172 (only one shown in FIG.1). As seen in FIGS. 7 and 8, the mounting member 152 further includes ahandle 173 that extends radially outwardly from the mounting member 152and is formed as a unitary part thereof.

As best seen in FIG. 1, the hull collector further includes a preformed,resilient seal 180 having a cylindrical portion 182 that blends into aplanar, ring-shaped flange portion 184 extending radially outward fromthe cylindrical portion 182, with both the cylindrical portion 182 andthe flange 184 centered on the axis 16. Four circumferentially spaceddeformable tabs 186 extend upwardly through mating slots 188 in themounting member 152 to engage the seal 180 with the mounting member 152.The cylindrical portion 182 has an interference fit with the cylindricalwall 168 of the bottom wall 160 and includes three ring-shaped ribs 190that engage the inner surface of the outer wall 91 of the vessel 90 torestrict the escape of heated air from the roasting chamber 12. Theplanar portion 184 engages a circular lip 190 of the vessel 90.

It should be appreciated that the seal 180 increases the efficiency ofthe coffee roasting apparatus by inhibiting the leakage of hot air fromthe coffee roasting apparatus.

Preferably, the bottom wall 160 is made from a stamped piece of suitablemetal, such as 430 stainless steel. This tends to reflect heat backtowards the roasting chamber 12 and serves to protect the mountingmember 152 and the lid 15 from overheating. Preferably, the mountingmember 152 is formed from a suitable high temperature plastic material,such as a phenolic plastic. It is preferable that the seal 180 be formedfrom a suitable high temperature resilient material, such as a suitableresilient silicon material.

The lid 15 includes a generally inverted cup shaped housing 200, aplanar, ring-shaped filter screen 202, a planar, generally ring-shapedfilter screen mount bracket 204, a handle 206, and a locking bracket208. The filter screen 202 is mounted against an upper surface of thehousing 200 by the bracket 204 and covers a hot air outlet in the formof four circumferentially extending and spaced slots 210 to preventhulls from exiting through the slots 210 with the hot air stream.Optionally, the lid 15 may include a plurality of relatively small sizedhot air outlets 211 immediately opposite the hot air inlet 163. Theoutlets 211 should be of a sufficiently small size to prevent asignificant amount of chaff from exiting through the outlets 211.Preferably, the outlets 211 are circular with a nominally 2 mm diameter.The outlets 211 act as a safety feature to prevent overheating of thecoffee roasting apparatus by providing an outlet for the hot air streamin the event that the filter screen 202 should become so blocked withchaff that the hot air stream would otherwise begin to stagnate andthereby overheat the coffee roaster.

The bracket 204 is retained to the housing 200 by four sets of resilientfinger flanges 212, each set engaging a cylindrical stub tab 214 thatextends downwardly from the cover 200. The locking bracket 208 and thehandle 206 are fixed to the housing 200 by a threaded fastener 216 thatextends through a hole in the bracket 208 to engage a threaded openingin the handle 206, thereby clamping the handle 206 and the bracket 208to the housing 200. The locking bracket 208 includes a pair ofdownwardly extending legs 218 (one shown rotated out of plane in FIG. 1)each of which terminates in a cylindrically shaped foot 220 that extendsin a radially outward direction. As best seen in FIG. 8, the feet 220are received through respective slots 222 in the innermost flange 162 ofthe bottom wall 160 so that the feet 220 can engage a bottom lip 224 ofthe flange 162 when the lid 15 is rotated relative to the collector 14to lock the lid 15 and the collector 14 together. The housing 200includes an annular shoulder 225 and a downwardly extending cylindricallip 226 that overlay the mounting member 152 to prevent the leakage ofhot air from the hull collector 14. A circumferentially extending notch227 is provided in the lip 226 to provide clearance for the handle 174of the hull collector 14, with the circumferential length of the notch227 being sufficient to allow the required relative rotation between thelid 15 and the hull collector 14 to engage and disengage the feet 220with the lip 224.

Optionally, a cylindrical filter 228 can be placed within the hullcollector 14 and the lid 15. The filter 228 includes an array ofopenings 227 of a size that is greater than the size of the openings inthe filter screen 202. This allows the filter 228 to filter relativelylarge size hulls and other chaff from the hot air stream as the hot airstream flows from the hot air inlet 163 to the hot air outlet 210,thereby preventing such larger size hulls and other chaff from cloggingthe filter screen 202. The filter screen 202 filters relatively smallersize hulls and other chaff from the hot air stream that are not removedby the filter 227.

As best seen in FIGS. 1 and 2, a control 230 is provided in the form ofthe temperature sensor 38 and an electronic circuit assembly 231 mountedto the control mounting panel 52 by a plurality of threaded fasteners232 (only one shown in FIG. 1). In this regard, it should be noted thatin the preferred embodiment the axis 21 of the heater/motor assembly 50is offset from the axis 16 of the coffee roasting apparatus to provideadequate clearance for the electronic circuit assembly 231. In someembodiments of the coffee roasting apparatus, this offset of the axes 21and 16 will not be required.

As best seen in FIG. 9, the electronic assembly 231 includes a pair ofLEDs 234 and 236 (only one shown in FIG. 1), a pair of switches 238 and240 (only one shown in FIG. 1), a rheostat 242, a programmable controlor chip 244, a relay 246, a TRIAC 248, and a resonator 249, all mountedon a printed circuit board 251 that electrically interconnects each ofthe aforementioned components. In the preferred embodiment, theprogrammable control 244 is provided in the form of a MICOM KS86C4104programmable control. The motor 18 and the heater 34 are powered bynormal household AC current (120 volt, 60 hertz) with the electroniccircuit assembly being provided suitable DC power in a known fashion bya bridge rectifier and regulator (not shown). The relay 246 is openedand closed in response to control signals from the programmable control244 in a known fashion to respectively de-energize and energize theresistance heater 34. The TRIAC 248 drives the motor 18 in a knownfashion at either a normal operating speed (nominally 12,000 rpm in thepreferred embodiment) or a cooling speed (nominally 15,000 rpm in thepreferred embodiment) that is greater than the normal operating speedbased on control signals from the programmable control 244. The normaloperating speed creates an air stream from the fan 22 to the roastingchamber 12 having a first velocity, and the cooling speed creates an airstream from the fan 22 to the roasting chamber 12 having a secondvelocity that is greater than the first velocity. The resonator 249provides a timing function to the control 230, as is known.

The rheostat 242 allows a user to input a setting to the control 230that determines the desired roasting cycle and that is maintained by thecontrol 230 between roasting cycles absent further manipulation of therheostat 242 by the user. In this regard, the control 230 can beprovided in two different configurations. In the first configuration, adesired roasting temperature T_(D) is preset in the coffee roaster, andthe user inputs a desired roasting time period t_(p) via the setting ofthe rheostat 242. Conversely, in the second configuration, the desiredroasting time period t_(p) is preset in the coffee roaster, and the userinputs the desired roasting temperature T_(D) via the setting of therheostat 242.

More specifically, in the first configuration, as shown in FIG. 10, auser activates the roasting switch 238 to initiate a roasting cycle, asshown at block 250. In response to activation of the switch 238, theprogrammable control 244 is configured to activate the LED 234 and todetect the setting, as shown at 251 and 252. As shown at 253A, thedetected setting is then used by the programmable control 244 todetermine and set a desired roasting time period t_(p) for the roastingcycle, with the desired roasting temperature T_(D) being preset in thecontrol 230 and thus independent of the setting of the rheostat 242.With respect to this configuration, in the preferred embodiment thepreset desired roasting temperature T_(D) is equal to 260° C. As shownat block 254, after the desired roasting time period t_(p) has beendetermined and set, the controller 230 initiates an operating mode thatis shown in FIG. 12 and discussed in more detail below.

In the second configuration, as seen in FIG. 11, after a user hasinitiated a roasting cycle by activating the roasting switch 238 atblock 250, the programmable control 244 activates the LED 234 anddetects the setting of the rheostat 242, as shown at 251 and 252. Asshown at block 253B, the detected setting is then used by theprogrammable control 244 to determine the desired roasting temperatureT_(D), with the desired roasting time period t_(p) for the roastingcycle being preset in the control 230 and thus independent of thesetting of the rheostat 242. With respect to this configuration, thepreset time period for the roasting cycle is preferably 15 minutes. Asshown at block 254, after the desired roasting temperature T_(D) isdetermined, the control 230 initiates the operating mode shown in FIG.12, which is the same for both of the above-discussed configurations ofthe coffee roasting apparatus.

It should be appreciated that the use of the rheostat 242 increases theconsistency from one roasting cycle to the next because it does notrequire a user to remember and/or accurately position a mechanical timeras in conventional coffee roasters. It should also be understood thatthe activation and deactivation of the LEDs 234 and 236 allow a user tovisually determine the operating status of the coffee roaster.

As seen by the logic diagram in FIG. 12, after entering the operatingmode, the programmable control 244 is configured to monitor theoperating status of the coffee roasting apparatus for every timeincrement t_(i). Upon entering the operating mode, the programmablecontrol 244 adds one time increment t_(i) to an elapsed time t_(e) forthe roasting cycle, as shown at the block 255. The programmable control244 then determines whether the elapsed time t_(e) is greater than thedesired roasting time period t_(p), as shown at 256. If the elapsedt_(e) does exceed the desired roasting time period t_(p), the control230 initiates a cool down cycle wherein the LED 234 is deactivated andthe LED 236 is activated, as shown at the block 257, and the heater 34is de-energized by opening the relay 246 and the motor 18 is driven atthe cooling speed for a predetermined cool down time period (5 minutesin the preferred embodiment), as shown at the block 258. After the cooldown time period has elapsed, operation of the coffee roasting apparatusis terminated, as shown at the block 259. A roasting cycle cannot bereinitiated by a user until after the cool down time period has expired.

If the elapsed roasting time t_(e) does not exceed the desired roastingtime period t_(p), the control 230 is configured to determine whetherthe switch 240 has been activated by a user during the roasting cycle.If the switch 240 has been activated, the control 230 initiates the cooldown cycle, as previously described and as shown at blocks 257, 258 and259. It should be appreciated that this feature allows a user toterminate a roasting cycle whenever the user desires, such as when thecoffee beans appear to the user to have achieved their desired roast, orwhen, for any other reason, the user wishes to discontinue operation ofthe coffee roaster.

As shown in the remainder of FIG. 12, for the active control of theroasting temperature T, the control 230 is configured to provide a “fanbased” control of the roasting temperature T to maintain the desiredroasting temperature T_(D). Specifically, the control 230 is configuredto obtain the desired roasting temperature T_(D) by cycling the motor 18between the normal operating speed and the cooling speed, whileminimizing cycling of the relay 246 to energize and de-energize theelectric heater 34. More specifically, the control is configured toinitiate a temperature control cooling mode wherein the heater 34 isenergized and the motor 18 is driven at the cooling speed for a fixedcooling time period t_(c) (10 seconds in the illustrated embodiment) toreduce the roasting temperature T when it exceeds the desired roastingtemperature T_(D).

In this regard, the control 230 is configured to monitor the roastingtemperature T based on the signal from the thermistor 38 and to initiatecertain operating modes for the heater 34 and the motor 18 based uponwhether the roasting temperature T is greater than or less than a numberof reference temperatures T_(S), T_(M), T_(D), and T_(L) as shown atblocks 261, 262, 264, and 266. The control monitors the roastingtemperature T at every time increment t_(i), which in the preferredembodiment is equal to one second.

The control first checks to see if the roasting temperature T exceeds asafety temperature T_(S) (290° C. in the illustrated embodiment), asshown at block 261. If the roasting temperature T is greater than thesafety temperature T_(S), the control 230 initiates the previouslydescribed cool down cycle, as shown at blocks 257, 258 and 259. Thisincreases the safety of the operation of the coffee roasting apparatusby terminating the heating of the coffee roasting apparatus andpreventing a reinitialization of the heating until after the cool downtime period has expired.

If the roasting temperature is less than the safety temperature T_(S),the control next determines whether the roasting temperature T isgreater than a max roasting temperature T_(M) (270° C. in the preferredembodiment), as shown at 262. If the roasting temperature T is greaterthan T_(M), the heater 34 is de-energized by opening the relay 246 forone time increment t_(i) (one second in the illustrated embodiment) andthe motor 18 is driven at the cooling speed for the time increment t_(i)to reduce the roasting temperature in a relatively abrupt fashion, asshown at block 276. The control process then returns to the block 255.

If the roasting temperature T is less than T_(M), the control 230 nextdetermines if the roasting temperature T exceeds the desired temperatureT_(D) (260° C. in the illustrated embodiment), as shown at the block264. If the roasting temperature T exceeds the desired temperatureT_(D), the control 230 then determines whether the temperature controlcooling mode has already been initiated, as shown at the block 278. Ifthe cooling mode has not been initiated, the control 230 initiates thetemperature control cooling mode by driving the motor 18 at the coolingspeed while the electric heater 34 is energized, as shown at 280 and282, and then returns to the block 255. If the temperature controlcooling mode has already been initiated, the control determines whetherthe cooling time period t_(c) has expired, as shown at the block 284. Ifthe cooling time period t_(c) has not expired, the motor 18 ismaintained at the cooling speed, while the heater is energized, as shownat the block 282. If the cooling time period t_(c) has expired, thetemperature control cooling mode is cleared by driving the motor at thenormal operating speed and de-energizing the heater 34 for one timeincrement t_(i) to further reduce the roasting temperature T, as shownat 286, and the control process returns to the block 255.

Returning to the block 264, if the roasting temperature T does notexceed the desired roasting temperature T_(D), the control 230determines whether the temperature control cooling mode is currentlyactive, as shown at the block 288. If the temperature control coolingmode is not currently active, the motor 18 is driven at the normaloperating speed and the heater 34 is energized, as shown at blocks 289and 290, and the control process returns to the block 255. If thetemperature control cooling mode is currently active, the control 230determines whether the roasting temperature T is less than a lowertemperature limit T_(L) (256° C. in the illustrated embodiment), asshown at the block 266. If the roasting temperature is less than thelower temperature limit T_(L), the temperature control cooling mode isdeactivated by driving the motor 18 at the normal operating speed withthe heater 34 energized, as shown at blocks 292 and 290, respectively.If the roasting temperature T is not less than T_(L), the control 230determines whether the cooling time period t_(c) has expired, as shownat the block 294. If the cooling period t_(c) has not expired, thetemperature control cooling mode is maintained by driving the motor 18at the cooling speed with the heater 34 energized, as shown at the block296, and the control process returns to the block 255. If the coolingperiod t_(c) has expired, the temperature control cooling mode isterminated by driving the motor 18 at the normal operating speed, withthe heater 34 energized, as shown at the block 298. The control thenreturns to the block 255.

It will be appreciated that the use of the “fan based” temperaturecontrol allows for a more accurate control of the roasting temperature Tin comparison to simply energizing and de-energizing the electricalheater 34 to control the roasting temperature T because of the thermalinertia typically associated with such electrical heaters 34. Further,it will be appreciated that the use of the “fan based” temperaturecontrol increases the operational life of the heater relay 246 byminimizing the opening and closing of the relay 246.

What is claimed is:
 1. A method of controlling the roasting temperaturein the roasting chamber of a hot air coffee roaster including anelectric heater and a fan that forces air past the heater to generate ahot air flow into the coffee roaster, the method comprising the stepsof: energizing the electric heater; driving the fan at a normaloperating speed; monitoring a temperature of the hot air flowing intothe roasting chamber; and driving the fan at a cooling speed that isgreater than the normal operating speed in response to said monitoredtemperature exceeding an upper temperature limit.
 2. The method of claim1 further comprising the step of returning the fan to the normaloperating speed from the cooling speed in response to said monitoredtemperature decreasing below a lower temperature limit.
 3. The method ofclaim 1 wherein the step of powering the fan at a cooling speedcomprises powering the fan at the cooling speed for a fixed time periodin response to said monitored temperature remaining above a lowertemperature limit for the fixed period of time.
 4. The method of claim 3further comprising the step of de-energizing the electric heater inresponse to said monitored temperature remaining above the uppertemperature limit for the fixed period of time.
 5. Apparatus forroasting coffee beans comprising: a housing having an air inlet; acoffee bean roasting chamber mounted to said housing; an electric motorwithin said housing; a fan in fluid communication with said roastingchamber and driven by the electric motor to create a roasting air streamto the roasting chamber; an electric heater within the housing to heatthe roasting air stream prior to the roasting air stream entering theroasting chamber; and a control for said motor, including a temperaturesensor located in said air stream downstream of said heater, saidcontrol operative to power the motor at a cooling speed in response tosaid sensor detecting a temperature greater than an upper temperaturelimit and to power the motor at a normal operating speed in response tosaid sensor detecting a temperature less than a lower temperature limit,said normal operating speed being less than said cooling speed.